JP2008207497A - Liquid ejection head and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein providing a damper surface wholly formed as a thin portion causes manufacturing malfunctions such as the occurrence of a pinhole failure etc., the inconvenience of handling. <P>SOLUTION: One wall surface of a common liquid chamber 8 has a lower rigidity than other wall surfaces, and serves as the damper surface 20 for alleviating pressure in the common liquid chamber 8. The damper surface 20 comprises a relatively thick part 21 formed of first-third layers 2a-c of an oscillating plate member 2 of the same material, and a relatively thin part 21 formed of the first layer 2a of the oscillating plate member 2. The thick and thin parts 21 and 22 are formed in a line shape which is elongated in the longitudinal direction of the damper surface. The line-shaped thin and thick parts 22 and 21 are alternately formed in the direction of the short side of the damper surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid discharge head and an image forming apparatus.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, and a multifunction machine of these, for example, a liquid ejection apparatus including a recording head composed of a liquid ejection head (droplet ejection head) that ejects liquid droplets of a recording liquid (liquid) As a liquid while transporting a medium (hereinafter also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, recording paper, etc. are also used synonymously). The recording liquid (hereinafter also referred to as ink) is attached to a sheet to form an image (recording, printing, printing, and printing are also used synonymously).

  The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. The term “not only” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium. Further, the liquid is not limited to the recording liquid and ink, and is not particularly limited as long as it is a liquid capable of forming an image. Further, the liquid ejection apparatus means an apparatus that ejects liquid from a liquid ejection head, and is not limited to an apparatus that forms an image.

  Such liquid ejecting apparatuses or image forming apparatuses have come to be used for industrial systems such as textile printing apparatuses and metal wiring. In recent years, it has been demanded that higher quality images can be output at a higher printing speed. Both the number and density of nozzles tend to increase with respect to the former requirement. Accordingly, the intervals between the pressurized liquid chambers are narrowed. In addition, the frequency of energy application tends to increase. In response to the latter requirement, attempts have been made to increase the length of the recording head, and recently, a so-called line-type head capable of covering the entire width of the recording medium has been put into practical use.

  The liquid discharge head includes a nozzle that discharges droplets, an individual liquid chamber (also referred to as a pressurized liquid chamber, a discharge chamber, a pressure chamber, and a liquid flow path) that communicates with the nozzle, and liquid in the pressure chamber. A pressure generating means (energy generating means) for generating pressure (energy) to be pressurized and a common liquid chamber having a relatively large volume for supplying a liquid to each pressure chamber; A liquid droplet is ejected from the nozzle by pressurizing the liquid. Here, as the pressure generating means, a thermal method using a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, a piezoelectric device (in this application, it is used as a synonym for an electromechanical transducer). There are known a piezoelectric method using an electrostatic method, an electrostatic method using an electrostatic actuator that generates an electrostatic force, and the like.

  By the way, in the liquid ejection head, when ejecting droplets, it is necessary to increase the pressure of the individual liquid chamber. The pressure generated here is propagated to the common liquid chamber at the same time as droplets are ejected from the nozzle. When this pressure is transmitted again to the individual liquid chamber side, it becomes a factor that causes the pressure in the individual liquid chamber to fluctuate to an unexpected value, and it becomes impossible to discharge the droplets at a desired droplet amount and speed, thereby causing ejection failure. In particular, when a plurality of individual liquid chambers are pressurized simultaneously and liquid droplets are ejected, the pressure transmitted from the individual liquid chambers to the common liquid chamber becomes very large, and injection failure tends to occur. In addition, if the pressure fluctuation propagated to the common liquid chamber propagates to the adjacent pressurized liquid chamber and causes mutual interference that affects the liquid, liquid droplets are unintentionally leaked and discharged, and the discharge state is unstable. Will be triggered. As a result, obtaining a high-quality image output is hindered.

  In order to prevent this, it is necessary to increase the pressure attenuation efficiency in the common liquid chamber. As a means for that, generally, a method is adopted in which the volume of the common liquid chamber is increased or a pressure absorber such as a diaphragm is provided on the wall surface of the common liquid chamber. In particular, a method using a pressure absorber is widely used because it can absorb pressure fluctuations without increasing the common liquid chamber size, and if an appropriate absorber is used, the pressure damping effect is very high. Further, as the pressure absorber, a part of the wall surface of the common liquid chamber is a member or structure having low rigidity and is attenuated by vibration of the wall surface itself, and a member having low elasticity such as rubber on the wall surface of the common liquid chamber There is a configuration in which the coating is attenuated by deformation of the surface of the member. Among these, the configuration that is attenuated by the vibration of the wall surface itself is particularly excellent because of the good attenuation efficiency.

For example, in Patent Document 1, when the direction in which a plurality of pressurized liquid chambers are arranged is the X direction, the wall surface extending in the X direction constituting the common liquid chamber has lower rigidity than other wall surfaces, and vibration It is described that a damper surface is formed by a pressure absorber that absorbs pressure, and the damper surface is not formed over the entire length of the common liquid chamber in the X direction, and a region where no damper surface exists is provided. Has been.
JP 2005-125631 A

Patent Document 2 describes that a pressure absorber is provided in a region between a pressure generation source (heater) in the individual liquid chamber and the common liquid chamber.
Japanese Patent Application Laid-Open No. 06-1991030 discloses that a common liquid chamber is provided with a plurality of pressure absorbers for absorbing pressure fluctuations, and an ink permeable filter is used to divide the pressure absorber chamber into two. . In Japanese Patent Laid-Open No. 2000-158668, a flexible film having flexibility is provided on at least one surface side of a reservoir communicating with the pressure generating chamber, and the flexible film is a piezoelectric material layer and both surfaces thereof. The flexible film includes a plurality of segments along a traveling direction of a bending wave in which at least one of the pair of counter electrodes propagates to the flexible film. And a head substantially including a plurality of driving elements is described. Japanese Patent No. 3695509

  However, when the rigidity of the wall surface of the common liquid chamber is lowered and formed as a thin film as described above, it is necessary to form a thin film over a wide area, so that process abnormalities such as pinholes are likely to occur and the manufacturing yield is increased. There is a problem of lowering. In addition, handling of the thin film during the manufacturing process becomes difficult. In particular, as represented by the line-type head described above, the head tends to increase in size due to the increase in the number of nozzles. In this case, the area of the pressure absorber is inevitably increased, and these construction problems are more serious. It has become.

  In addition, as described in Patent Document 2, it is difficult to sufficiently reduce the rigidity of the pressure absorber and to perform effective pressure absorption by providing the pressure absorber in units of individual liquid chambers. Become. Moreover, there exists a subject that a construction method becomes complicated if the pressure absorber chamber is divided into a plurality as described in Patent Document 3.

  The present invention has been made in view of the above problems, and a liquid discharge head capable of obtaining an effective pressure damping effect while improving problems in the manufacturing process, and a high-quality image can be obtained at high speed by including this liquid discharge head. An object of the present invention is to provide an image forming apparatus that can be formed by the above method.

  In order to solve the above problems, in the liquid discharge head according to the present invention, at least one wall surface among the wall surfaces forming the common liquid chamber is a damper surface having lower rigidity than the other wall surfaces. The damper surface includes a thick part made of the same material and a thin part having a relatively large thickness, and the thick part and the thin part are formed in a line extending in the longitudinal direction of the damper surface. The line-shaped thin portions and the line-shaped thick portions are alternately formed in the damper surface short direction.

  Here, it is preferable that there are two or more line-shaped thick portions. Moreover, it is preferable that at least one of the line-shaped thick part and the line-shaped thin part is divided at at least one place in the longitudinal direction of the damper surface. In this case, the outermost periphery of the damper surface is constituted only by the thin part. It is preferable. The damper surface may be formed of a Ni two-layer structure.

  An image forming apparatus according to the present invention includes the liquid ejection head according to the present invention.

  According to the liquid discharge head according to the present invention, at least one wall surface among the wall surfaces forming the common liquid chamber is a damper surface having lower rigidity than the other wall surfaces, and the damper surface is made of the same material. The thick part and the thin part include a relatively thin part, and the thick part and the thin part are formed in a line shape extending in the longitudinal direction of the damper surface. Since the thick line-shaped parts are alternately formed in the short direction of the damper surface, the efficient pressure damping effect is improved while improving the problems in the manufacturing process such as the occurrence of pinhole defects and inconvenience of handling. can get.

  The image forming apparatus according to the present invention includes the liquid ejection head according to the present invention, so that stable droplet ejection characteristics can be obtained and a high-quality image can be formed.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, a first embodiment of a liquid discharge head according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional explanatory view along the liquid chamber longitudinal direction (direction perpendicular to the liquid chamber arrangement direction) of the liquid discharge head, and FIG. 2 is a cross-section along the liquid chamber short direction (liquid chamber arrangement direction). FIG. 3 is an explanatory diagram of the same head as seen from the common liquid chamber side. The hatching in FIG. 3 is for facilitating distinction and does not represent a cross section.

  The liquid discharge head includes a flow path member (liquid chamber substrate) 1, a vibration plate member 2 bonded to the lower surface of the flow path member 1, and a nozzle plate 3 bonded to the upper surface of the flow path member 1. As a result, individual flow paths (hereinafter also referred to as “pressure liquid chambers”) 6 that communicate with the nozzles 4 that discharge liquid droplets (liquid droplets) are formed, and the diaphragm member 2 is provided in each pressure liquid chamber 6. A common liquid chamber 8 for supplying ink (recording liquid) as a liquid via the communication portion 9 and the communication passage 10 formed in the flow path member 1 and the fluid resistance portion 7 is formed in a frame member 17 described later.

  Here, the flow path member 1 is formed by anisotropically etching a single crystal silicon substrate having a crystal plane orientation (110) using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), thereby allowing each pressurized liquid chamber 6 or Openings and grooves such as the fluid resistance portion 7 and the communication passage 10 are formed. In addition, the flow path member 1 can also form each pressurization liquid chamber 6 etc. by carrying out mechanical processing, such as etching or punching, using an acidic etching liquid, and the flow path member 1 can also be formed. 1 and the nozzle plate 3 or the diaphragm member 2 can be integrally formed by electroforming. Other photosensitive resins can also be used.

  The diaphragm member 2 is formed of a nickel plate having a three-layer structure of the first layer 2a, the second layer 2b, and the third layer 2c from the pressurized liquid chamber 6 side, and is manufactured by electroforming, for example. As the diaphragm member 2, for example, a laminated member of a resin member such as polyimide and a metal plate such as a SUS substrate, or a member formed from a resin member can be used.

  The nozzle plate 3 forms a large number of nozzles 4 corresponding to the pressurized liquid chambers 6 and is bonded to the flow path member 1 with an adhesive. As this nozzle plate 3, what consists of metals, such as stainless steel and nickel, resin, such as a polyimide resin film, silicon | silicone, and those combinations can be used. Further, the inner shape (inner shape) of the nozzle 4 is formed in a horn shape (may be a substantially cylindrical shape or a substantially frustum shape), and the hole diameter of the nozzle 4 is a diameter on the ink droplet outlet side of about 20 to. 35 μm.

  Further, a water repellent treatment layer having a water repellent surface treatment (not shown) is provided on the nozzle surface (surface in the ejection direction: ejection surface) of the nozzle plate 3. Examples of the water-repellent treatment layer include PTFE-Ni eutectoid plating, fluororesin electrodeposition coating, vapor-deposited fluororesin (e.g., fluorinated pitch), silicon resin / fluorine resin A water-repellent film selected according to the recording liquid physical properties such as baking after solvent coating is provided to stabilize the droplet shape and flight characteristics of the recording liquid and to obtain high quality image quality.

  The diaphragm member 2 includes a second layer 2b and a third layer at the center of a diaphragm portion (vibration region) 2A that is a deformable region formed by the first layer 2a corresponding to each pressurized liquid chamber 6. Convex portions 2B having a layered structure of layers 2c are formed, and laminated piezoelectric elements 12A constituting pressure generating means (actuator means) are respectively joined to the convex portions 2B.

  The plurality of piezoelectric elements 12A are formed in one piezoelectric element member 12 in a comb-tooth shape without being divided by half-cut groove processing (slit processing). The piezoelectric element member 12 includes a plurality of piezoelectric elements. It is fixedly arranged on the base member 13 along the arrangement direction of 12A. In this case, the plurality of piezoelectric elements arranged in a row are the piezoelectric elements 12A that are driven alternately and the piezoelectric elements 12B that are not driven that serve as simple struts. The piezoelectric element 12B serving as the support column is joined to a portion corresponding to the liquid chamber interval wall 6A.

  The piezoelectric element member 12 includes, for example, a lead zirconate titanate (PZT) piezoelectric layer having a thickness of 10 to 50 μm / layer and an internal electrode layer made of silver / palladium (AgPd) having a thickness of several μm / layer. The electrodes are alternately stacked, and the internal electrodes are alternately electrically connected to the individual electrodes and the common electrodes, which are end electrodes (external electrodes) on the end surfaces. The vibration region 2A is displaced by the expansion and contraction of the piezoelectric element 12A whose piezoelectric constant is d33 (d33 indicates the expansion / contraction perpendicular to the internal electrode surface (thickness direction)), and the liquid chamber 6 contracts and expands. ing. When the drive signal is applied to the piezoelectric element 12A and charging is performed, the piezoelectric element 12A expands, and when the charge charged in the piezoelectric element 12A is discharged, the piezoelectric element 12A contracts in the opposite direction.

  It should be noted that the ink in the pressurized liquid chamber 6 may be pressurized using a displacement in the d33 direction as the piezoelectric direction of the piezoelectric element member 12, or may be pressurized using a displacement in the d31 direction as the piezoelectric direction of the piezoelectric element member 12. A configuration may be adopted in which the ink in the liquid chamber 6 is pressurized. In the present embodiment, a configuration using displacement in the d33 direction is adopted.

  The base member 13 is preferably formed of a metal material. If the material (material) of the base member 13 is a metal, heat storage due to self-heating of the piezoelectric element member 12 can be prevented.

  Further, a frame member 17 is joined around the diaphragm member 2 with an adhesive. In the frame member 17, a common liquid chamber 8 that supplies liquid to each liquid chamber 6 is formed. A liquid (recording liquid) is supplied from the common liquid chamber 8 to the liquid chamber 6 through the communication portion 9 formed in the diaphragm member 2. The frame member 17 is also formed with a recording liquid supply port for supplying a recording liquid from the outside to the common liquid chamber 8.

  The common liquid chamber 8 is formed in a rectangular shape with a planar shape in the direction in which the pressurized liquid chambers 6 are arranged (nozzle arrangement direction: this is referred to as “the common liquid chamber longitudinal direction”). Of the wall surfaces forming the common liquid chamber 8, at least one wall surface is formed by the first layer 2 a of the diaphragm member 2, so that rigidity is higher than other wall surfaces formed by the frame member 17. The damper surface 20 is low.

  As shown in FIG. 3, the damper surface 20 includes a thick portion 21 formed by the first layer 2 a to the third layer c of the diaphragm member 2 and a relatively thick thickness portion 21 of the diaphragm member 2. The thin portion 21 formed by the one layer 2a is relatively thin, and the thick portion 21 and the thin portion 22 are formed in a line extending in the damper surface longitudinal direction (same as the common liquid chamber longitudinal direction). Has been. The thick portion 21 and the thin portion 22 are both formed of the same material by being formed of the diaphragm member 2.

  And here, the line-shaped thin part 22 and the line-shaped thick part 21 are alternately formed in a damper surface short direction (it becomes a direction orthogonal to a nozzle arrangement direction), as shown in FIG. . In this example, the number of line-shaped thick portions 22 is five, but this is not a limitation.

  The thick portion 21 may have a two-layer structure and the thin portion 22 may have a one-layer structure, or the thick portion 21 may have a three-layer structure and the thin portion 22 may have a two-layer structure. In addition, it is preferable that at least the common liquid chamber 8 side of the diaphragm member 2 forming a part of the wall surface of the common liquid chamber 8 has ink resistance (liquid resistance).

  In the liquid ejection head configured as described above, for example, the voltage applied to the piezoelectric element 12 is lowered from the reference potential, the piezoelectric element 12 contracts, and the diaphragm 2 descends to expand the volume of the pressurized liquid chamber 6. Thus, the ink flows into the pressurized liquid chamber 6, and then the voltage applied to the piezoelectric element 12 is increased to extend the piezoelectric element 12 in the stacking direction, and the diaphragm 2 is deformed in the nozzle 4 direction to pressurize the liquid. By contracting the volume / volume of the chamber 6, the recording liquid in the pressurized liquid chamber 6 is pressurized, and droplets of the recording liquid are ejected (jetted) from the nozzle 4.

  Then, by returning the voltage applied to the piezoelectric element 12 to the reference potential, the diaphragm 2 is restored to the initial position, and the pressurized liquid chamber 6 expands to generate a negative pressure. The pressurized liquid chamber 6 is filled with a recording liquid. Therefore, after the vibration of the meniscus surface of the nozzle 4 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (drawing-pushing), and striking or pushing can be performed depending on the direction of the drive waveform. Strike is to lower the potential from the reference potential, contract the piezoelectric element, increase the internal volume of the pressurized liquid chamber, and then return the potential to the reference potential, thereby returning the diaphragm to the initial position and ejecting droplets. The hitting method and the pressing method are methods of discharging droplets by raising the potential from a reference potential and pushing the diaphragm into the pressurized liquid chamber side.

  When pressure fluctuations are generated in the pressurized liquid chamber 6 in order to discharge droplets from the nozzle 4 in this manner, the pressure fluctuations in the pressurized liquid chamber 6 are changed to the fluid resistance portion 7, the communication path 10, and the communication portion 9. It is transmitted to the common liquid chamber 8 through. As a result, a pressure fluctuation occurs in the common liquid chamber 8, but the propagated pressure fluctuation is attenuated by the vibration of the damper surface 20. The droplet cannot be ejected at the droplet volume and the droplet velocity, or the pressure in the pressurized liquid chamber 6 that does not eject the droplet is changed to break the nozzle meniscus, so that the recording liquid leaks or the droplet is ejected. Therefore, droplet discharge can be performed stably.

  And in this embodiment, since it is set as the structure by which the line of the thin part 22 and the line of the thick part 21 are alternately formed in the damper surface short direction on the damper surface 20, it is thin by the presence of the thick part 21. Although the area of the portion 22 is reduced and the occurrence of defects and abnormalities in the manufacturing process such as pinholes is reduced, the thick portion 21 is formed in a line shape in the longitudinal direction of the damper surface. The pressure absorption effect which is almost the same as the case of 22 can be obtained. Moreover, since the thick part 22 becomes a pillar which supports the damper surface 20, the strength is increased and the handling in the manufacturing process becomes easy.

  The widths of the thick part 21 and the thin part 22 may be equal or different. Further, the area of the region constituting the thick portion 21 and the area of the region constituting the thin portion 22 are most preferably approximately the same, but the present invention is not limited to this. Moreover, in the said embodiment, although it is set as only two types of thickness of the thick part 21 and the thin part 22, it can also be set as three or more types of thickness.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is an explanatory plan view of the head damper surface as viewed from the common liquid chamber side in the same embodiment.
In this embodiment, two line-shaped thick portions 21 are formed, and these line-shaped thick portions 21 and the damper surface are formed alternately in the short direction. Even with such a configuration, the same effects as those of the first embodiment can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is an explanatory plan view of the head damper surface as viewed from the common liquid chamber side in the same embodiment.
In this embodiment, in the said 2nd Embodiment, it is set as the structure by which the line-shaped thick part 21 is divided | segmented in two places (it is not restricted to two places but may be three or more places) in the damper surface longitudinal direction. .

  When comprised in this way, the rigidity of a longitudinal direction can fall and the pressure absorption effect can be heightened compared with the said 2nd Embodiment. However, the effect of the thick portion 21 as a column is reduced, and the strength of the damper surface 20 itself is lowered. This configuration is a structure suitable when the length of the damper surface 20 in the longitudinal direction is short.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is an explanatory plan view of the head damper surface as viewed from the common liquid chamber side in the same embodiment.
In this embodiment, in the second embodiment, the ribs 23 formed by the thick portion 21 in the damper surface short direction with respect to the line-shaped thick portion 21 are not limited to two locations (not limited to two locations, It may be formed at three or more locations.)

  When configured in this manner, the strength of the damper surface 20 is improved as compared with the second embodiment, but the rigidity in the short direction is increased. This configuration is suitable when the length in the longitudinal direction of the damper surface is long, particularly in the case of a configuration such as a line type head. Even if several ribs 23 are formed, if the distance between the ribs 23 is sufficient, the effect as a damper (pressure absorption effect) functions sufficiently.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is an explanatory plan view of the head damper surface as viewed from the common liquid chamber side in the same embodiment.
In this embodiment, in the second embodiment, the line-shaped thick portion 21 is not formed up to the end in the longitudinal direction of the damper surface 20, and the outer peripheral portion of the damper surface 20 is a thin portion 22.

  When configured in this manner, the strength of the damper surface 20 decreases, but the displacement of the damper surface 20 at the outermost peripheral portion can be increased, and therefore, the integral of the displacement amount of the entire damper surface 20, that is, the deformation of the damper surface 20. Thus, the volume change of the common liquid chamber 8 can be increased, and the pressure absorption effect can be enhanced.

Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 8 is an explanatory plan view of the head damper surface as viewed from the common liquid chamber side in the same embodiment.
In this embodiment, three line-shaped thick portions 21 are provided, and the line-shaped thick portions 21 are divided at two locations in the longitudinal direction of the damper surface (not limited to two locations, but may be three or more locations). Further, the line-shaped thick portion 21 is not formed up to the longitudinal end of the damper surface 20, and the outer peripheral portion of the damper surface 20 is a thin portion 22.

Next, a seventh embodiment of the present invention will be described with reference to FIG. FIG. 9 is an explanatory plan view of the head damper surface as viewed from the common liquid chamber side in the same embodiment.
In this embodiment, four line-shaped thick portions 21 are provided in the second embodiment.

Next, the effect of this invention is demonstrated in contrast with a comparative example.
First, a general example of the flow path configuration will be described. In the first example shown in FIGS. 10 and 11, a plurality of liquid chamber units 101 including the nozzles, liquid chambers, pressure generating means, and the like described above are arranged side by side, and each is connected to the common liquid chamber 102 via the communication portion 103. It is connected. The common liquid chamber 102 is formed in the frame member 105, and one surface thereof is a damper surface 104. In the second example shown in FIGS. 12 and 13, the liquid chamber unit 101, the communication portion 103, and the common liquid chamber 102 are arranged in a straight line.

  The liquid chamber unit 101 includes a liquid chamber, a nozzle, a pressure conversion unit, and the like. Here, the pressure conversion means may be a piezoelectric actuator that discharges liquid droplets by applying a voltage to the electrostrictive element and deforming the electrostrictive element, or generates heat by flowing a current through the electrothermal conversion element. Thus, it is possible to provide a thermal actuator that ejects liquid droplets by foaming the liquid. In addition, an electrostatic actuator may be used.

  When a piezoelectric actuator is used, droplets of various sizes can be ejected by adjusting the deformation amount of the piezoelectric element, which is advantageous for forming an image with good gradation. On the other hand, when a thermal actuator is used, it is easy to achieve high integration of slurs. Therefore, it is suitable for a multi-nozzle head and is advantageous for forming an image with high resolution at high speed.

  The liquid chamber unit 101 may be an edge shooter system in which the shape from the flow path to the nozzle (discharge port) is linear, or a side shooter system in which the flow path direction and the nozzle (discharge port) direction are different. It may be. The edge shooter type head has the advantage that it is extremely easy to miniaturize each part with precision, make the nozzles multi-sized and downsize, and is excellent in mass productivity. On the other hand, there is a limit to the response frequency and droplet flight speed during droplet ejection. In addition, when a thermal actuator is used, bubbles are generated in the liquid due to the heat generated by the electrothermal transducer, but the actuator contracts due to the impact when the bubbles shrink due to a decrease in temperature and disappear near the electrothermal transducer. As a result, a cavitation phenomenon occurs in which the head is gradually destroyed. In particular, since this phenomenon is remarkable in the edge shooter method, the life of the head becomes relatively short.

  On the other hand, the head of the side shooter type has a structural advantage that energy can be converted more efficiently into kinetic energy of droplet formation and flight, and meniscus can be quickly returned by liquid supply. Even when a thermal actuator is used, the bubbles grow, and when the bubbles reach the nozzle, the bubbles are communicated with the atmosphere. have.

  In the above-described flow path configuration, the damper surface 104 normally has a direction in which the liquid chamber units 101 are arranged, that is, in FIG. 10 and FIG. In an actual head, the liquid chamber units 101 are arranged in several tens to several hundreds of rows, and the damper surface 104 has a shape in which the longitudinal direction is remarkably long with respect to the short side direction, that is, the aspect ratio is large. For this reason, when the damper surface 104 has a structure in which the rigidity in the short side direction is increased, the pressure damper effect is rapidly reduced.

  Further, as described above, the longitudinal direction is very long and the required area of the damper becomes large. Therefore, when the damper surface 104 is formed as a thin film as a whole, the problem of yield reduction due to pinholes occurs as described above. Therefore, the whole is not made a thin film, but it is preferable to have a two-layer structure of a thick part and a thin part as in the present invention. However, it is necessary to adopt a configuration in which the pressure relaxation effect does not decrease due to the presence of the thick portion. Therefore, the thick part and the thin part line run in the longitudinal direction, and the thick part penetrates in the longitudinal direction by adopting a configuration in which the thick part and thin part lines are alternately arranged in the short direction. Therefore, although the rigidity in the longitudinal direction is structurally increased, the longitudinal direction is sufficiently long, and even if such a thick portion is running, the deformation of the damper surface is not actually greatly affected. Also, in the short direction, the damper surface can be sufficiently deformed by the presence of the thin portion without the thick portion being continuous.

  In order to confirm this effect, the following five types of damper surfaces were prepared, and the pressure absorption effect of the common liquid chamber was confirmed. The result is shown in FIG. In FIG. 15, the long one-dot chain line indicates Comparative Example 1, the two-dot chain line indicates Comparative Example 2, the one-dot chain line indicates Example 1, the broken line indicates Example 2, and the solid line indicates Example 3.

Comparative Example 1: The entire damper surface has a thickness of 26 μm (the shape shown in FIG. 14).
Comparative Example 2: The entire damper surface is 3 μm thick (shape shown in FIG. 14)
Example 1: Thick part 26 μm, thin part 3 μm, one line of thick part Example 2: thick part 26 μm, thin part 3 μm, thick part 2 lines (shape of FIG. 4)
Example 3: Thick part 26 μm, thin part 3 μm, thick part 5 lines (shape of FIG. 3)

  All the components other than the damper surface are unified. Moreover, in the structure of the comparative example 3 and Example 1, 2, the area of a thick part and a thin part is the same (each 1/2 of the whole damper surface). FIG. 15 evaluates the pressure value of the common liquid chamber when the head is driven by changing the drive frequency.

  In FIG. 15, the peak near 2.4 kHz is the frequency of the primary resonance of the entire head. In the comparative example 1, the common liquid chamber pressure also shows a large value due to the head resonance, but in the comparative example 2, the resonance at this frequency is considerably reduced due to the pressure damper effect. In Examples 1, 2, and 3, the area of 3 μm in thickness is halved as compared with Comparative Example 2, but a sufficient pressure reduction effect substantially the same as Comparative Example 2 is ensured.

  Furthermore, in the case of the comparative example 2, although the value of 2.4 kHz is small, a large resonance point that cannot be seen elsewhere is generated at other frequencies (1 kHz, 4.7 kHz, etc.). This is due to resonance of the damper surface itself. In Comparative Example 2, since the rigidity of the damper surface is low, a large number of such resonance points appear at a relatively low frequency. On the other hand, in Examples 1, 2, and 3, resonance of the damper surface itself hardly occurs in the low frequency region, and therefore hardly occurs.

  However, in the case of Example 1 with one thick part, the pressure resonance suppression effect at 2.4 kHz, that is, the pressure fluctuation suppression effect at the time of head resonance is insufficient compared to Examples 2 and 3. Therefore, the number of lines in the thick part is preferably 2 or more.

  As described above, in the low-frequency region that is an actual head driving frequency band, the effect is higher than when the entire damper surface is configured to be thin. Further, since the area of the thin portion is reduced as compared with Comparative Example 2, the yield reduction due to pinholes can be improved as compared with Comparative Example 2. Furthermore, as shown in FIG. 4, if the thick wall portion is formed over the entire length of the damper surface, this becomes a pillar, which also has the effect of suppressing breakage of the damper surface (film breakage, etc.) during processing and driving. is there.

  Next, as another example, as shown in FIG. 16, FIG. 17 shows the result of comparing the embodiment of the present invention with the case where the thin portion is formed at the end and the thick portion is formed at the center. In FIG. 17, the long one-dot chain line indicates Comparative Example 3, the two-dot chain line indicates Comparative Example 4, the one-dot chain line indicates Comparative Example 5, the broken line indicates Example 4, and the solid line indicates Example 5.

Here, the shape is as follows so that the total area of the thin portion changes.
Comparative Example 3: Thin portion; length 10 mm in the longitudinal direction, length 2 mm in the short direction,
Total area: 10 × 2 × 2 (both ends) = 40 mm ²
Comparative Example 4: Thin portion; length in the longitudinal direction 15 mm, length in the short direction 2 mm,
Total area: 60mm ²
Comparative Example 5: Thin portion; length in the longitudinal direction 20 mm, length in the short direction 2 mm
Total area: 80mm ²
Example 4: Thick part; number of lines 4 (length 54.4 mm x width 250 mm)
Total area: 55.2 mm ²
Example 5: Thick part: 4 lines (length 54.4 mm x width 350 mm)
Total area: 33.4 mm ²

  Here, Comparative Examples 4, 5, and 6 have shapes as shown in FIG. 16, and Examples 4 and 5 have shapes shown in FIG. In all cases, the dimensions of the entire damper surface are 54.8 mm × 2 mm, the thickness of the thick portion is 26 μm, and the thickness of the thin portion is 3 μm.

According to FIG. 17, in the configurations of Comparative Examples 4 to 6, in Comparative Examples 4 and 5, when the total area of the thin portion is 60 mm ² or less, a large resonance peak remains in the vicinity of 2 kHz. It is necessary to expand the area to about 80 mm ² . On the other hand, in Examples 4 and 5, a sufficient resonance suppression effect is obtained even in Example 3 having a total area of 33.4 mm ² . That is, even when the two-layer structure of the thick part / thin part is adopted, the total area of the thin part can be reduced by adopting the configuration of the present invention, and the yield reduction of pinholes and the like can be further suppressed. Can do.

Next, a specific example of the first embodiment will be described.
Si having a height of 500 μm is used as the flow path member 1, and a pressurized liquid chamber 6 having a height of 100 μm, a length of 1000 μm in the longitudinal direction, and a width of 170 μm in the lateral direction is formed thereon. A nozzle plate 3 having a thickness of 20 μm is formed by Ni electroforming. The diaphragm 2 has a three-layer structure by Ni electroforming, and has a thickness of 3 μm (first layer 2a), 11.5 μm (second layer 2b), and 11.5 μm (third layer 2c) from the liquid chamber 6 side. To do. The diaphragm 2 forms the damper surface 20 in the same layer.

  The piezoelectric element 12A is used as the pressure generating means, and this is fixed to the base member 13, and the pressurized liquid chamber 6 is pressurized via the connecting portion 2B. The piezoelectric element 12A has a 16-layer laminated structure in which silver and palladium electrodes are sandwiched between the upper and lower sides.

  The common liquid chamber 8 is formed in a frame member 17 made of epoxy resin, and has a depth of 3000 μm, a short direction length (length in the horizontal direction in FIG. 1) 2600 μm, and a long direction length (in FIG. Vertical length) is 54000 μm.

  As shown in FIG. 3, the damper surface 20 has five thick portions 21 and has a length in the longitudinal direction of 54000 μm and a length in the short direction of 2000 μm. The thick portion 21 has a width of 200 μm, and is formed side by side at equal intervals in the short direction of the damper surface 20. The thickness of the thick portion 21 is 26 μm, and the thickness of the thin portion 22 is 3 μm.

  As a comparative example, a head having the same configuration and a damper surface 20 of all 3 μm was also manufactured.

  The head according to the first embodiment and the head according to the comparative example were mounted on a printer, and a printing test was performed. As a result, when printing was performed by ejecting ink from all the nozzles, a good result was obtained with a printer equipped with the head according to the present invention without causing defective image quality. The printer had poor image quality. Moreover, the yield in the diaphragm member forming step is also higher in the present invention, and the improvement effect of the present invention was confirmed.

Next, a specific example of the sixth embodiment will be described.
Si having a height of 500 μm is used as the flow path member 1, and a pressurized liquid chamber 6 having a height of 100 μm, a length of 1000 μm in the longitudinal direction, and a width of 170 μm in the lateral direction is formed thereon. A nozzle plate 3 having a thickness of 20 μm is formed by Ni electroforming. The diaphragm 2 has a three-layer structure by Ni electroforming, and has a thickness of 3 μm (first layer 2a), 11.5 μm (second layer 2b), and 11.5 μm (third layer 2c) from the liquid chamber 6 side. To do. The diaphragm 2 forms the damper surface 20 in the same layer.

  The piezoelectric element 12A is used as the pressure generating means, and this is fixed to the base member 13, and the pressurized liquid chamber 6 is pressurized via the connecting portion 2B. The piezoelectric element 12A has a 16-layer laminated structure in which silver and palladium electrodes are sandwiched between the upper and lower sides.

  The common liquid chamber 8 is formed on a frame member 17 made of epoxy resin, and has a depth of 2000 μm, a short direction length (length in the left-right direction in FIG. 1) 2600 μm, and a long direction length (in FIG. Vertical length) is 32000 μm.

  As shown in FIG. 8, three thick portions 21 divided in the middle are formed on the damper surface 20. The damper surface 20 has a length in the longitudinal direction of 32000 μm and a length in the short direction of 2000 μm. The thick portion 21 has a width of 300 μm, and is formed at equal intervals in the short direction of the damper surface 20. The thickness of the thick portion 21 is 26 μm, and the thickness of the thin portion 22 is 3 μm. Further, the thick portion 21 is divided into three equal parts in the longitudinal direction of the damper surface 20, and the length per one is 10000 μm. Further, the end portion in the longitudinal direction of the damper surface 20 does not reach the thick portion 21, and the outermost periphery of the damper surface 20 is formed only by the thin portion 22.

  As a comparative example, a head having the same configuration and a damper surface 20 of all 3 μm was also manufactured.

  The head according to the sixth embodiment and the head according to the comparative example were mounted on a printer, and a printing test was performed. As a result, when printing was performed by ejecting ink from all the nozzles, a good result was obtained with a printer equipped with the head according to the present invention without causing defective image quality. The printer had poor image quality. Moreover, the yield in the diaphragm member forming step is also higher in the present invention, and the improvement effect of the present invention was confirmed.

Next, an example of an image forming apparatus including the liquid ejection apparatus according to the present invention including the liquid ejection head according to the present invention will be described with reference to FIGS. FIG. 18 is a schematic configuration diagram for explaining the overall configuration of the mechanism portion of the apparatus, and FIG. 19 is a plan view of a principal portion of the mechanism portion.
This image forming apparatus is a serial type image forming apparatus, and a carriage 233 is slidably held in the main scanning direction by main and sub guide rods 231 and 232 which are guide members horizontally mounted on the left and right side plates 201A and 201B. The main scanning motor that does not perform moving scanning in the direction indicated by the arrow (carriage main scanning direction) via the timing belt.

  The carriage 233 has recording heads 234a and 234b (which are composed of liquid ejection heads according to the present invention for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). When not distinguished, it is referred to as “recording head 234”). A nozzle row composed of a plurality of nozzles is arranged in the sub-scanning direction orthogonal to the main scanning direction, and is mounted with the ink droplet ejection direction facing downward.

  Each of the recording heads 234 has two nozzle rows. One nozzle row of the recording head 234a has black (K) droplets, the other nozzle row has cyan (C) droplets, and the recording head 234b has one nozzle row. One nozzle row ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets.

  The carriage 233 is equipped with head tanks 235a and 235b (referred to as “head tank 35” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 234. The sub tank 235 is supplementarily supplied with ink of each color from the ink cartridge 210 of each color via the supply tube 36 of each color.

  On the other hand, as a paper feeding unit for feeding the paper 242 stacked on the paper stacking unit (pressure plate) 241 of the paper feed tray 202, a half-moon roller (feeding) that separates and feeds the paper 242 one by one from the paper stacking unit 241. A separation pad 244 made of a material having a large coefficient of friction is provided opposite to the sheet roller 243 and the sheet feeding roller 243, and the separation pad 244 is urged toward the sheet feeding roller 243 side.

  In order to feed the sheet 242 fed from the sheet feeding unit to the lower side of the recording head 234, a guide member 245 for guiding the sheet 242, a counter roller 246, a conveyance guide member 247, and a tip pressure roller. And a conveying belt 251 which is a conveying means for electrostatically attracting the fed paper 242 and conveying it at a position facing the recording head 234.

  The conveyor belt 251 is an endless belt, and is configured to wrap around the conveyor roller 252 and the tension roller 253 so as to circulate in the belt conveyance direction (sub-scanning direction). In addition, a charging roller 256 that is a charging unit for charging the surface of the transport belt 251 is provided. The charging roller 256 is disposed so as to come into contact with the surface layer of the conveyor belt 251 and to rotate following the rotation of the conveyor belt 251. The transport belt 251 rotates in the belt transport direction when the transport roller 252 is rotationally driven through timing by a sub-scanning motor (not shown).

  Further, as a paper discharge unit for discharging the paper 242 recorded by the recording head 234, a separation claw 261 for separating the paper 242 from the transport belt 251, a paper discharge roller 262, and a paper discharge roller 263 are provided. A paper discharge tray 203 is provided below the paper discharge roller 262.

  A duplex unit 271 is detachably mounted on the back surface of the apparatus body 1. The duplex unit 271 takes in the paper 242 returned by the reverse rotation of the transport belt 251, reverses it, and feeds it again between the counter roller 246 and the transport belt 251. The upper surface of the duplex unit 271 is a manual feed tray 272.

  Further, a maintenance / recovery mechanism 281 including a recovery means for maintaining and recovering the nozzle state of the recording head 234 is disposed in the non-printing area on one side in the scanning direction of the carriage 233. The maintenance / recovery mechanism 281 includes cap members (hereinafter referred to as “caps”) 282a and 282b (hereinafter referred to as “caps 282” when not distinguished) for capping each nozzle surface of the recording head 234, and nozzle surfaces. A wiper blade 283 that is a blade member for wiping the ink, and an empty discharge receiver 284 that receives liquid droplets for discharging the liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid. ing.

  In addition, in the non-printing area on the other side in the scanning direction of the carriage 233, the liquid that receives liquid droplets when performing idle ejection that ejects liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. An ink recovery unit (empty discharge receiver) 288 that is a recovery container is disposed, and the ink recovery unit 288 includes an opening 289 along the nozzle row direction of the recording head 234 and the like.

  In this image forming apparatus configured as described above, the sheets 242 are separated and fed one by one from the sheet feeding tray 202, and the sheet 242 fed substantially vertically upward is guided by the guide 245, and is conveyed to the conveyor belt 251 and the counter. It is sandwiched between the rollers 246 and conveyed, and further, the leading end is guided by the conveying guide 237 and pressed against the conveying belt 251 by the leading end pressing roller 249, and the conveying direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately applied to the charging roller 256, that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 251 alternates, that is, in the sub-scanning direction that is the circumferential direction. , Plus and minus are alternately charged in a band shape with a predetermined width. When the sheet 242 is fed onto the conveyance belt 251 charged alternately with plus and minus, the sheet 242 is attracted to the conveyance belt 251, and the sheet 242 is conveyed in the sub scanning direction by the circumferential movement of the conveyance belt 251.

  Therefore, by driving the recording head 234 according to the image signal while moving the carriage 233, ink droplets are ejected onto the stopped paper 242 to record one line, and after the paper 242 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 242 has reached the recording area, the recording operation is finished and the paper 242 is discharged onto the paper discharge tray 203.

  In such a serial type image forming apparatus, by including the liquid discharge apparatus according to the present invention including the liquid discharge head according to the present invention, stable droplet discharge can be performed and a high-quality image can be formed at high speed. Can do.

Next, another example of an image forming apparatus including a liquid ejection apparatus provided with a liquid ejection head according to the present invention will be described with reference to FIG. FIG. 20 is a schematic configuration diagram of the image forming apparatus.
This image forming apparatus is a line type image forming apparatus provided with a full line type head. The image forming apparatus includes an image forming unit 402 and a transport mechanism 403 for transporting paper inside the apparatus main body 401. A paper feed tray 404 on which a large number of paper sheets 405 can be stacked is provided. After the image is recorded, the paper 405 is discharged onto a paper discharge tray 406 mounted on the other side of the apparatus main body 401.

  The image forming unit 402 is a liquid discharge head according to the present invention that has a liquid tank that contains a liquid as a recording liquid and has a nozzle row corresponding to the length in the paper width direction (direction perpendicular to the transport direction). The line type heads 410y, 410m, 410c and 410k are provided. These line type heads 410y, 410m, 410c, 410k are attached to a head holder (not shown).

  The line-type heads 410y, 410m, 410c, and 410k discharge droplets of each color in the order of, for example, yellow, magenta, cyan, and black from the upstream side in the sheet conveyance direction. As the line-type head, a single head in which a plurality of nozzle rows that discharge droplets of each color are arranged at a predetermined interval can be used, or a head and a liquid cartridge can be used separately. .

  The sheets 405 in the sheet feeding tray 404 are separated one by one by a sheet feeding roller 421, fed into the apparatus main body 401, and sent to the transport mechanism 403 by a sheet supply roller 422.

  The transport mechanism 403 has a transport belt 425 stretched between the driving roller 423 and the driven roller 424, a charging roller 426 for charging the transport belt 425, and the transport belt 425 facing the image forming unit 2. A recording liquid wiping member (here, a cleaning roller) composed of a guide member (plastic template) 427 for guiding part and a porous body as a cleaning means for removing the recording liquid (ink) attached to the conveying belt 425 428, a neutralizing roller 429 mainly composed of conductive rubber for neutralizing the sheet 405, and a sheet pressing roller 430 for pressing the sheet 405 toward the conveying belt 425.

  Further, on the downstream side of the transport mechanism 403, a paper discharge roller 431 for sending the paper 405 on which an image is recorded to the paper discharge tray 406 is provided.

  Also in the line type image forming apparatus configured as described above, by feeding the sheet 405 by charging the conveyance belt 425, the sheet 405 is attracted to the conveyance belt 425 by electrostatic force and conveyed by the circular movement of the conveyance belt 425. Then, an image is formed by the image forming unit 402 and discharged to the discharge tray 406.

  In such a line type image forming apparatus, by providing the liquid ejection apparatus according to the present invention including the liquid ejection head according to the present invention, stable droplet ejection can be performed, so that a high-quality image is formed at high speed. be able to.

  The image forming apparatus according to the present invention can be applied to, for example, an image forming apparatus such as a printer / fax / copier single function machine or a multifunction machine thereof. Further, the present invention can also be applied to an image forming apparatus that uses a recording liquid or a fixing processing liquid that is a liquid other than ink, and other liquid ejecting apparatuses that eject various liquids as described above.

FIG. 3 is an explanatory cross-sectional view along the liquid chamber longitudinal direction (direction orthogonal to the liquid chamber arrangement direction) showing the first embodiment of the liquid discharge head according to the present invention. FIG. 6 is a cross-sectional explanatory view along the liquid chamber short direction (liquid chamber arrangement direction) of the head. It is the plane explanatory view which similarly saw the damper surface of the head from the common liquid chamber side. FIG. 10 is an explanatory plan view of a damper surface in a second embodiment of the liquid ejection head according to the present invention as viewed from the common liquid chamber side. FIG. 10 is an explanatory plan view of a damper surface in a third embodiment of the liquid ejection head according to the present invention as viewed from the common liquid chamber side. FIG. 9 is an explanatory plan view of a damper surface in a fourth embodiment of the liquid ejection head according to the present invention when viewed from the common liquid chamber side. FIG. 10 is an explanatory plan view of a damper surface in a fifth embodiment of the liquid ejection head according to the present invention when viewed from the common liquid chamber side. FIG. 10 is an explanatory plan view of a damper surface in a sixth embodiment of the liquid discharge head according to the present invention when viewed from the common liquid chamber side. FIG. 10 is an explanatory plan view of a damper surface in a seventh embodiment of the liquid ejection head according to the present invention as viewed from the common liquid chamber side. FIG. 6 is a schematic explanatory diagram illustrating a first example of a flow path configuration in a liquid discharge head. It is typical explanatory drawing which follows the AA line of FIG. It is a typical explanatory view explaining the 2nd example of channel composition in a liquid discharge head. It is typical explanatory drawing which follows the BB line of FIG. FIG. 7 is an explanatory plan view of a damper surface in the liquid discharge heads of Comparative Examples 1 and 2 when viewed from the common liquid chamber side. FIG. 6 is an explanatory diagram showing measurement results of head driving frequency and pressure value of a common liquid chamber in the liquid ejection heads of Comparative Examples 1 and 2 and Examples 1 to 3. FIG. 10 is an explanatory plan view of a damper surface of the liquid ejection heads of Comparative Examples 3 to 5 as viewed from the common liquid chamber side FIG. 10 is an explanatory diagram showing measurement results of head drive frequency and pressure value of a common liquid chamber in the liquid ejection heads of Comparative Examples 3 to 5 and Examples 4 and 5. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. It is a schematic block diagram which shows the other example of the image forming apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Channel member 2 ... Vibration plate member 2A ... Vibration area 2B ... Island-shaped convex part 3 ... Nozzle plate 4 ... Nozzle 6 ... Pressurizing liquid chamber (pressure chamber)
DESCRIPTION OF SYMBOLS 7 ... Fluid resistance part 8 ... Common liquid chamber 12 ... Piezoelectric element 13 ... Base member 20 ... Damper surface 21 ... Thick part 22 ... Thin part 23 ... Rib 234a, 234b ... Recording head 410k, 410c, 410m, 410y ... Line type head

Claims (6)

A plurality of pressurized fluid chambers, a common fluid chamber in which each pressurized fluid chamber is connected via a communication port, and a pressure converting means for changing the pressure in the pressurized fluid chamber, and communicates with the pressurized fluid chamber. In a liquid ejection head that ejects liquid droplets from the nozzle
Among the wall surfaces forming the common liquid chamber, at least one wall surface is a damper surface having lower rigidity than the other wall surfaces,
The damper surface includes a thick part having a relatively large thickness and a thin part having a relatively small thickness made of the same material.
The thick part and the thin part are formed in a line extending in the longitudinal direction of the damper surface,
The liquid discharge head, wherein the line-shaped thin portions and the line-shaped thick portions are alternately formed in the short side direction of the damper surface.   The liquid discharge head according to claim 1, wherein there are two or more line-shaped thick portions.   3. The liquid ejection head according to claim 1, wherein at least one of the line-shaped thick portion and the line-shaped thin portion is divided at at least one point in a longitudinal direction of the damper surface. Liquid discharge head.   4. The liquid discharge head according to claim 3, wherein an outermost periphery of the damper surface is constituted only by the thin portion.   5. The liquid discharge head according to claim 1, wherein the damper surface has a two-layer structure of Ni.   6. An image forming apparatus for forming an image by discharging droplets from a liquid discharge head, comprising the liquid discharge head according to claim 1.

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